Conversion of hydrocarbon oils



Aug. 14, 1945'.

Vw. M. STRATFORD4 CONVERSIO OF HYDROCARBON OILS Filed June 4. 1942IIHHHHHHU HHHHUHHHI Patented Aug.l14, 194s UNITED STAT Es #PATE NT'oFFicE CONVERSION OF HYDROCABBON OILSv William M. Stratford, New York,N.

to The Texas Compan poration of Delaware Y.; assignor y, New York, N.Y., a cor- Application June 4, 1942, Serial No. 445,701

(ci. 19e-52) 3 Claims.

.of a catalyst.

'I'he present application is a continuation-inpart of my pendingapplication, Serial No. 267,840,

led April 14, 1939.

In the conversion of hydrocarbon oils wherein the oil is subjected tohightemperatures for sufficient time to effect cracking, there is`usually recombination or polymerization of unsaturated materials toform products which tend to produce heavy undesirable bodies, such astar or coke. For this reason it is customary in thermal cracking to heatthe oil as quickly as possible to a cracking temperature and then 'allowthe cracking reaction to take place i'n a large zone wherein depositionof coke may take place.

In the catalytic cracking of oils the oil is heated lto aconversiontemperature and the vapors contacted with a catalyst for asuilicient length of time to produce the desired cracking reaction. Manyoi the' active cracking catalysts promote polymerization and the contactof the oil. with the catalyst vlor an` appreciable length of timeprovides yau opportunity for substantial polymerization to take place.Whether the caus is' due to polymerization is not definitely known, butin any event, itis common experience that the catalyst becomes coatedwith carbon and requires regeneration at frequent intervals. v

According to the present invention, the oil to be cracked is raised to ahigh cracking temperature in excess of that normally used or necessaryto obtain cracking and then the hot oil contacted with a catalyst for avery short and controlled period of time. At such elevated temperaturesthe cracking reaction takes place much more rapidly and only a shorttime ofV contact is necessary whereby formation of coke is substantiallyretarded. The eiiiciency of the catalyst accordingly is maintained at ahigh level during its residence in the reaction zone.

The present invention may be conducted Iby heating the. oil to a highcracking temperature as quickly as possible, preferably withoutsubstantial cracking. The heating may take place in a direct lirefurnace wherein the oil is passed through tubes of suitable size and atthe proper rate to obtain a high cracking temperature quickly andpreferably near the exit of the coil. If desired, other means of rapidheating may be used, for example, iiuid baths such as hot molten metal,for example, lead. y

The temperature to which the oil may be heated in the heating stage willvary, depending on the type of oil, but it is advantageous to heat theoill to temperatures in the range 900 to 1100 F., the catalyticconversion being carried out ata temperature in this range. l

The hot oil is contacted preferably in the vapor phase with au activecracking catalyst under conditions ysuch that a very vshort andcontrolled time of contact may be obtained.

The time of contact of the oil with the catalyst will vary'but should besufficiently low that substantially no thermal cracking occurs. lOrdinarl ilyin catalytic cracking the time should be less vthan about10() seconds. In the present process the time is considerably less thannormally used even for catalytic cracking as practiced heretofore.According to the present invention, wherein the oil is heated to a hightemperature, the time of contact with the catalyst may be cut down to1/2 or evenl t/a the time normally required for catalytic cracking.

In .accordance with the present invention the residence time of thecatalyst within the reaction zone may be substantially less than that ofthe heated oil vapor, particularly when operating in the mannerillustrated in the drawing whereinl a stream of solid catalyst particlescontinually moves through the reaction zone. The residence time of thecatalyst advantageously doesnot exceed one minute and preferably Vissubstantially less than one minute. For example, the residence time iorthe catalyst may range from about 1 to 7 .seconds or may be as low as afraction of a second, while the residence time of the heated oil withinthe reaction zone may range from about 2 to 15 seconds.

Where it is desired to maintain a time of contact between hydrocarbonsand catalyst of the order of one second or less the residence time ofthe hydrocarbons within the reaction zone may be approximately orslightly greater than that of the catalyst. On the other hand theresidence time of the hydrocarbon may range from 1% to 4 or 5 times thatof the catalyst.

It is contemplated that the higher the reaction temperature the shorterwill be the residence time for bo'th oil and catalyst within thereaction zone.

According to one advantageous mode of operation the oil vapor heated tothe reaction temperature flows downwardly through an enlarged verticalreaction zone. The catalyst in solid particle form is also introducedcontinuously to the top 0I the reaction zone 'and drops through thezone. While dispersed throughout the oil vapor both hydrocarbon andcatalyst are continuously removed from the bottom or lower portion ofthe reaction zone.

The ratio of catalyst to oil within the reaction zone may be less than 1or as much as 4 or 5 to 1 lor even 20 to 1. i

The particle size and density affects the rate of catalyst fall throughthe reaction zone so that by suitable sizing of the catalyst particlesand also depending upon the manner of injection in the reaction zoneconsiderable variation in the residence time of the catalyst within thereaction zone may be secured.

If desired a horizontal reaction vessel may be employed through whichthe hydrocarbon vapors iiow in a horizontal direction, While thecatalyst particles ow in a substantially vertical direction. By havingthe horizontal dimension relatively great as compared to the verticaldimension of the reaction zone the residence time of the hydrocarbonsmay be relatively great compared to that of the catalyst.

'I'he time of exposure of the catalyst andoil to the high crackingtemperature is controlled by regulating the time the catalyst and oil isin the reaction zone, and then quickly quenching the oil to atemperature sufciently low to arrest the reaction. 'I'he quenching ispreferably accomplished by injecting a cooling medium such as oil,

for example, gas oil or naphtha or other oil suit- -able as a charge tothe unit, or a product from the unit, including recycle stock or othermaterial of higher boiling point than naphtha.

'Ihe quenched hydrocarbon reaction products are fractionatedto recoverthe cracked ,naphthal while the withdrawn catalyst is regenerated andrecycled to the reaction.

Any well known or preferred type of catalyst may be used. Specicmaterials contemplated are highly adsorptive clays, such as acid treatedclays, for example, Filtrol or Super-Filtrol, or other acid treatedmontmorillonites or bentonites; Activated Alumina; natural or artiilcialzeolites or similar base exchange adsorptive may terials; silica gel, orother adsorptive silica alone or coated with an oxide of certain metalsof 'groups DI and IV, such as alumina or zirconia,

or an oxide of a metal of group VI, such as an oxide of chromimolybdenum or tungsten; or mixtures of oxides of groups III, IV and VI,such as mixtures of oxides of aluminum or zirconium and chromium ormolybdenum.

'I'he process may be carried out at substantially atmospheric pressureor slightly above, such as 50 or 100 pounds. Also various gases may beintroduced to retard side reactions and carbon formation, such ashydrogen, nitrogen, water vapor `and the like.

The invention will be more fully understood from the followingdescriptionread in connection with the accompanying drawing which showsone form of apparatus for carrying out the process of the invention.

Referring to the drawing. charge oil is introduced by the pump I throughthe line 2 to a heating coil 3, wherein the oil is raised to a highcracking temperature. The products are then transferred through a line 5to a reaction chamber 6. The supply of catalyst is contained 1in achamber 8 in a suitable form, such as a slurry, whereby it mayHVV bepumped by the pump 8 through the line I0 and injected into the reactionchamber. The reaction products are withdrawn from the lower portion ofthe reaction chamber through the line I2 and contacted with a quench oilintroduced through the line I4 by the pump I5.

The mixture at a temperature below cracking is then introduced into aseparator I6. In the separator the catalyst separates out and iswithdrawn from thelower portion thereof through the line I8 and may berecycled to the reaction chamber 6 by the pump I9fthrough the line 20.Preferably the catalyst is passed through the line 2| -to a catalystregeneration plant 22. This plant is shown diagrammatically and mayconsist of a filter for filteringvthe heavy oil from the catalyst andsuitable means for removing the carbon from the catalyst, for example byburning or roasting. The regenerated catalyst is then conducted throughthe line 25 to the catalyst chamber 8.

Hydrocarbon vapors are passed from the upper portion of the separator I6through the line 26 to a. fractionator 28, wherein the insufficientlycracked products are separated from vapors containing a gasolinefraction. The high boiling fraction collecting in the lower portion ofthe fractionator 28 is withdrawn through the linel 30 and may berecycled to the heating coil 3 for further cracking or withdrawn fromthe system for further use, such as a charge for thermal cracking or asa fuel oil. The vapors containing gasoline and lighter constituents arepassed overhead from the fractionator 28 through vapor line 32 andcondenser 33 to a receiver 36.

An important advantage of the method of flow illustrated in the drawinginvolves providing a. relatively short residence time for the catalystwithin the reactor. The residence time for the catalyst is less than forthe hydrocarbons in the reactor because the catalyst particles fallthrough the hydrocarbon vapors in the reactor by difierence in densityarriving at the outlet from the 40 reactor before the hydrocarbons withwhich the catalyst entered. Since the hydrocarbon vapors and catalystparticles both ow in a downward direction the rapid descent of thecatalyst particles is facilitated. Accordingly, the catalyst `particlesactually remain in the reaction zone a substantially shorter time thanthe hydrocarbons which are undergoing conversion.

Thus, the decline in catalyst activity is substantially reduced sincelessl time Iwithin the reaction zone is afforded for deposition ofcarbon on the catalyst particles. By regenerating all of the withdrawncatalyst prior to its return to the top of the reactor all of thecatalyst actually within the reactor is thus maintained at a very highstate of activity during the entire time that it is within the reactor.

Efiecting conversion by the action of a catalyst which remains at a highlevel of actitvity during the entire period of residence in the re actoris advantageous from the standpoint of' producing high octane gasolinewhich has a high lead susceptibility. It appears. that catalytic con- Yversion under these conditions favors the hydrogen transfer reactionwhereby naphthene hydrocarbons are converted to aromatics and hydrogenand the resulting hydrogen is ultilized to combine with olefins formedfrom the conversion of other constituents of the feed. As a consequencethere is produced a more saturated gasoline product of high octanevalue.

Instead of introducing the catalyst to the reactor in the form of aslurry, it maybe introduced in dry, solid form and provisionv may bemade for its separate removal from the bottom of the reactor inrelatively dry form.

Obviously y modications and variations of the invention, as hereinbeioreset forth. may be made without departing fromthe spirit and scopethereof, and therefore only such limitations should be imposed as arelindicated in the appended claims.

I claim:

1. A continuous process for the catalytic cracking of hydrocarbonswherein both hydrocarbons and catalyst now through a reaction zone, thecatalyst being recycled all or in part to produce high octane gasolinehydrocarbons which comprises passing a stream of gas oil in vapor phaseto a reaction zone maintained at a temperature in the range about 900 to1100 F., continuously introducing a nely divided solid catalyst inhighly active form to said reaction zone, maintaining feed hydrocarbonvapor and catalyst in brief and intimate contact within the zone, saidcontact being made in the substantial absence of recycled catalyst whichhas not been regenerated.' y maintaining the residence time of thecatalyst within the reaction zone in the range from a fraction of asecond to about 7 seconds, maintaining the residence time of hydrocarbonwithin the reaction zone greater than that of the catalyst but not morethan about 11/2 to 5 times that of the catalyst. continuouslywithdrawing reacted and unreacted hydrocarbons and continuouslywithdrawing catalyst from the reaction zone While still in a state ofhigh activity. l

2. A continuous process for the catalytic conversion of hydrocarbonswhich comprises heating gas oil to a temperature in the range 900 to.

1100 F. without substantial cracking,continuouslypasslngastreamotsaidheatedssoilin vapor phase through areaction zone at a temperature within the aforesaid range. continuous-1y passing through the reaction zone a highly active solid catalyst innely divided form. maintaining the catalystl residence time within thereaction zone in the range from a fraction of a second to about sevenseconds and substantially A within the aforesaid range, continuouslypassing through the reaction zone a highly active solid catalyst infinelyk divided form, maintaining the catalyst residence time within thereaction zone in the range from a fraction of a second to about 7,seconds, maintaining the hydrocarbon residence time within the reactionzone greater than that oi.' the' catalyst but not more than-about 1% to5 times that of the catalyst. continuously withdrawing reacted andunreacted hydrocarbons from the reaction zone, and continuouslywithdrawing catalyst from the reaction zone while still in a state ofhigh activity.

WILLIAM M. S'I'RA'IFORD.

